


Insatiable

by snasational



Series: Raffle Prizes [4]
Category: Undertale (Video Game)
Genre: Breeding, Consensual Somnophilia, Crosstale Sans (Undertale), M/M, Vaginal Sex
Language: English
Status: Completed
Published: 2021-02-11
Updated: 2021-02-11
Packaged: 2021-03-17 22:33:52
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,229
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29358045
Author URL: https://archiveofourown.org/users/snasational/pseuds/snasational
Summary: Cross is always horny. Sans is always tired. Luckily for Cross, Sans has a solution.
Relationships: Sans/Sans (Undertale)
Series: Raffle Prizes [4]
Series URL: https://archiveofourown.org/series/2081718
Comments: 14
Kudos: 146





	Insatiable

**Author's Note:**

  * For [TheSinBubble](https://archiveofourown.org/users/TheSinBubble/gifts).



> Welp! I’ve never posted something on my phone before, so I hope this works out. And many apologies to TheSinBubble. I’m sorry this took so long to get out! 
> 
> Not Beta’d or proofread. Sorry for any mistakes!

Lately, Cross is in a constant state of horniness. Out of this world horny, to be exact. The first thing he wants when he wakes up is sex, and the last thing he wants to do before bed is sex. He doesn’t know why he’s been in this kind of mood, because his heat isn’t due for another three months and he shows no other signs of it starting. Plain and simple; he just wants to fuck. And Sans, bless his heart, is just along for the ride. 

However, it’s easy to forget how different they are. Sans is much older than him and in terms of libido he gets worn out way faster than Cross. Cross could go round after round if he wanted to, but Sans barely makes it through the first one before he’s tapping out. And that’s okay, usually. The last thing Cross would ever want to do is push Sans into sex he doesn’t want to have. It’s not enjoyable for either party.

There are also days where Sans doesn’t want to get out a bed, let alone partake in a physical activity like fucking. (If you asked Cross, they could both use the exercise. His ecto is getting much rounder than he ever would’ve allowed in the past.) During those days, Cross rolls off the mattress and rubs one out in the shower, giving Sans much needed privacy and rest. It’s the least he could do for his partner. 

Masturbation doesn’t provide Cross with  _ any  _ relief though. Now that he’s had a taste of regular sex, it’s easy to say that it’s become an addiction of sort. He craves it like he’s never craved something before and watching his cum float down the drain only makes him feel miserable. It should be splattered across his ribcage or buried deep in Sans, not clogging up the pipes. 

It’s a dangerous line of thinking. Cross isn’t entitled to it; he knows that. And yet these awful thoughts keep consuming him. It almost feels like he’s dying from it. Like there’s some terrible horrible sex demon possessing his body and making him think such nasty things. Never in his life had fucking been a big deal until now and honestly he’s surprised Sans hasn’t put a stop to it.

But the thing with Sans is that he just seems amused by the whole ordeal. Not upset, not put off, just...deeply humored. Like Cross told him the funniest joke in the entire world. As if Cross’ misfortune is something to be laughing at. 

“Buddy, it’s not a big deal.” Sans assures him before bed. “You’re young. Being young and horny go hand in hand.”

Cross huffs and folds his arms. They’re both under the covers, so Sans doesn’t see this action. It’s the thought that counts. 

“It can’t be easy on you.” He insists. 

Sans chuckles. “I’ll be alright. If I didn’t want you on top of me, you wouldn’t be there.”

Well. Cross has never actually seen Sans fight anyone but he certainly believes it. Maybe it’s the air of mystery the dude is surrounded with but he’d never want to step on his toes. Although, Sans is so chill about everything that he can’t imagine him getting worked up enough to fight someone. Which also makes him concerned that Sans wouldn’t say no even if he really didn’t want it. 

Ugh. So much conflict and it’s all because of his stupid dick.

“Okay.” Cross says dejectedly. 

“Hey now, don’t sound so  _ cross  _ with me.”

Despite himself, Cross smiles. “You’ve already used that one before.”

“Oops. I guess it’s hard to be original when you’re in a relationship with your clone.” 

Ah, here comes those insufferable butterflies that make him feel fuzzy. They haven’t labeled their relationship before, but when Sans acknowledges it Cross gets so unbelievably happy. He feels like he doesn’t deserve this. Not after everything he’s done. But Sans is kind, and loving, and supportive. Without him Cross would’ve been lost to all of the anger and bitterness. And so would Chara. 

He saved them both, really. Even if Chara doesn’t like to admit it. But Chara’s been dormant for quite some time, so it’s not like he can get his opinion on anything right now. Which he counts as a blessing, because Chara knowing about his struggle with the beast that is his horniness would be mortifying. 

“I’m the cool Sans.” Cross points out after a moment. “So was I really your clone to begin with?”

Sans snorts. “Are you implying that I’m not cool?”

“You sleep and drink ketchup all day. And you’re old. And you snore. Loudly.” Cross hums for a second, pretending to be in thought. “Oh! You haven’t done your laundry in two months and have resorted to stealing mine. That’s pretty lame, dude.” 

Sans sighs dramatically. “Can’t please everybody. But ya know, I have loads of fans. Way more than you do, buddy.” 

“Puh-lease. Your fanclub consists of me and Papyrus and that drunk chick at the bar.” 

“Oh? So you admit that you’re a fan and that I  _ am  _ cool?” Sans teases. Cross groans and rolls over, tugging the sheets over his head. 

“No. Goodnight.” 

“Well this is new. You don’t wanna go a round before bed?” Sans shuffles until he’s closer to him. 

Cross fights back a blush; the concern in his voice is both flattering and humiliating. Flattering because he cares, humiliating because he’s on an obvious schedule. But he can’t help it, the lust has become engraved into his very soul. And it’s not just for anyone, either. All Cross wants is Sans. He wants to be inside him, he wants to be fucked by him, he wants to spend hours eating him out, he wants to hear him sob in ecstasy as Cross fucks him through orgasm after orgasm. Trying to think of anybody else just reverts to him circling back to Sans. 

“Do you?” Cross deflects. 

“I asked you first.”

Cross anxiously plays with the comforter. “I can go without.” 

“Didn’t we just talk about this?” Sans apparently can’t keep the amusement out of his voice. Cross pouts. 

“You’re tired. I know you are, because you’re always tired. So go to sleep. We fucked this morning anyways, i’ll be fine without.” 

“Hm.” Sans says nonchalantly. “Well, you know, just kinda throwing it out there. I’m okay with you having fun at night.” 

“No, I’m going to let you sleep.” 

“And who said I had to be awake?” 

Cross freezes. Sans yawns and snuggles deeper into the bed. Like he didn’t just drop a bomb on Cross’ head. Is Sans implying that he’d be okay with Cross…? He shudders. His pelvic bones begin to tingle slightly at the thought. Throughout their sex life, the two of them have done many interesting things. Usually spanned out through different sessions because Sans passes out after cumming once; regardless they’ve gotten around to some interesting things. 

“Anyways, goodnight.” Sans mumbles sleepily. Cross doesn’t hear him, too hung up on what was just said to comprehend anything else. 

Logically, vanilla sex while Sans sleeps isn’t as kinky as the time Sans- well. If he wants to tame the horniness, perhaps he shouldn’t think of  _ that.  _ But despite this, the idea of it is incredibly dirty and taboo. Cross squirms a bit, struggling to get comfortable after Sans gave him the green light for something so...perverse, for a lack of better words. 

“Sans, I-”

A loud, unattractive snore interrupts him. Cross cringes at the sound of it. How can someone who doesn't even have to breathe snore like that? He’s starting to think that Sans does it on purpose. And on top of that, how can he fall asleep so quickly after saying something like that? He snores again, pulling Cross from his musings.

Frowning, Cross rolls back over to face Sans. True enough, his face is slack and his jaw is slightly unhinged. Sans’ sleeping face isn’t actually all that different from his resting face; relaxed and cozy looking. Cross has always admired that about him. The way he never seems stressed no matter what’s going on. He’s almost jealous of it.

“Are you really asleep?” Cross whispers. Nothing but loud, steady snoring answers him. 

He squirms some more. The tingling in his bones still lingers. If he allowed it, something would eagerly begin to form. But apprehension coils inside of him. What if his words were just a joke? Usually, Sans’ pranks aren’t serious in nature. Surely he wouldn’t play around about something like  _ this?  _

Sans used a word once...enigma? Something like that. It applies to him well. 

Instinctively, he reaches out and wipes away the drool that’s begun to slide down his chin. What a messy sleeper. If Cross didn’t adore Sans he would’ve thought it to be disgusting. Sans doesn’t budge an inch at the contact. 

Maybe...maybe he was dead serious. Maybe Cross could…

He slides his hand upwards to cup Sans’ cheekbone. He’s warm to the touch, comfortably so. Whenever he snores, it makes Cross’ phalanges tingle in a ticklish manner. A devilish thought enters his head; would the rest of Sans shake? Would it cause tremors inside of his cunt? Would it make him clench down hard on his dick? 

His hand moves from his cheek to the vertebrae of his neck. Still no reaction. Cross inhales. By now, he’s used to the smell of ketchup. However, he never thought the condiment would be able to invoke so much lust. Is it weird that he gets turned on by it now? 

“Why’d it have to be ketchup?” He muses out loud. Sans shivers the lower Cross traces. “Why couldn’t you like normal smelling things? Like chocolate?” 

He breathes in deeply again. Faintly, Sans  _ does  _ smell like chocolate. That’s only because he’s wearing Cross’ clothes, though. They really need to sort through his laundry some time; Cross is quickly running out of his own clothing. For some reason, it’s his socks that seem to be disappearing the fastest. 

Sans says something, but it’s garbled from sleep. He scoots closer to Cross, his phalanges coming up to grasp Cross’ t-shirt with an iron tight grip. Nothing unusual; Sans is like a koala bear during the night. It draws a fond smile on Cross’ face. He’s so much more affectionate when he isn’t awake. Cross doesn’t take it personally. Sans is a private person who shows his love through other means.

The soft atmosphere is broken when Sans unconsciously shoves his leg in between Cross’ thighs. He makes a strangled noise when the other’s patella makes contact with his groin. It’s already overly sensitive from the unformed magic but the extra friction gives it the last edge it needed. Instead of a cock, an aching cunt conjures. It’s unexpected but not unwelcome. Cross isn’t picky, as long as he’s getting off he’s happy. 

He can’t believe he’s actually doing this. Cross squeezes around the leg and grinds down. Sans’ kneecap presses against his clit roughly. With a stifled moan, Cross wraps his arms around Sans and pulls him closer to his ribcage as he begins to repeat the motion. 

His shorts begin to dampen, and the more he grinds the wetter the sound gets. Warm pressure builds in his newly formed stomach, and after a few more moments of his desperate grinding it crests. Cross moans low in Sans’ ear, but the sound is drowned out by the skeleton’s snores. 

His hips give a few more twitches before he slumps into Sans’ embrace. The orgasm was nice, and it sent pleasant static throughout his bones, but it still isn’t enough. That restlessness persists, the desire to cum over and over again making the first orgasm of the night weak.

And, judging from the way something hard pokes into his stomach, Sans just might be experiencing the same restlessness as him. He plants a kiss on his skull before maneuvering Sans onto his back. From this position, he can see the faint blue glow seeping through Sans’ pants. Well, technically  _ his _ pants. 

“Look at you.” Cross cooes, speaking words he’d never say if Sans was awake. “Already hard. Even in your sleep you can’t resist me, huh? All I did was hump you a little. Maybe you’re secretly just as bad as me.” 

He snakes his hand between them and palms at Sans’ bulge. It twitches underneath his touch, eliciting a pleased noise from Cross. Knowing that Sans reacts to his touch even in his sleep makes him feel prideful. 

Cross lets go of Sans dick to shimmy out of his shorts. He tosses them in the corner, on top of Sans’ overflowing laundry basket. It’s so full that you can’t even see the basket anymore, so maybe it’s best to call it a laundry mountain. Now that his pants are gone, his wet pussy can finally breathe. Wearing clothes when he’s horny makes him feel like he’s on fire, and not in the good way.

“I was going to fuck you, you know. But I really need you inside of me.” He scoots down Sans’ body until he’s straddling his hips. That wonderful bulge pressed against his bare cunt. 

Impulsively, he grinds down once just to feel the solidness of him. He doesn’t repeat the action though; he’s much too impatient for any further teasing. Instead he hooks his fingers in Sans’ shorts and yanks them down just enough for his cock to spring out. Sans shifts a bit, but otherwise stays unconscious. Cross reckons he’ll be awake soon enough. If he sleeps through getting his dick rode Cross will be thoroughly impressed. But maybe not surprised. He’d sleep through a hurricane, if you let him. 

He grips onto his dicks and lowers his hips, guiding the bulbous tip to his entrance. Wasting no further time, Cross sinks down and lets out a sultry moan. He makes him so full; Sans is thick and long. He hits all the best places inside of Cross. He really ought to start bottoming more, Sans’ dick is heavenly. 

“You were made for me.” He tells Sans earnestly. He reaches down and grabs Sans’ wrists, pulling them to settle on his hips. Sans doesn’t seem to need much encouragement, because they tighten into his ecto-flesh harshly. Good, Cross likes the way it stings a bit. 

Satisfied, he begins to roll his hips. The slide burns in the best way possible. If Sans was awake, he’d summon a knife and beg him to press it against his neck. Sans is the best about trying crazy things as long as there’s no actual pain involved. One of these days Cross will get Sans to hurt him, but for some reason Sans is adamantly against it.

He braces his hands on Sans’ sternum and begins to bounce hard and fast. Pressure starts to build up again, much faster than it did last time. He’s so lost in the sensation that he doesn’t notice Sans blink open his eye sockets. 

“Heh.” Sans breathes out. His voice is husky from the sleep. “You actually took me up on that offer, huh?” 

Cross doesn’t stop bouncing. Sans has made no indication that he’s displeased by what’s going on, so why would he stop? This feels too amazing. Bottoming has always tended to reduce him into a mindless mess and now is no different. Sometimes, when Sans has the energy, he’ll fuck him so silly that he can’t even remember his name. 

“Was I not supposed too?” He pants out. Sans’ dick jabs against a spot that has him seeing stars. It causes him to clench down hard, resulting in the two of them groaning simultaneously. 

“Ngh, fuck. You can do whatever you want.” Sans rubs circles into the indents he left behind on Cross’ hips. Soothing and apologetic. 

“You’re too good for me.” Cross murmurs. Sans smiles up at him. He looks tired, but the adoration on his face shines through that. It makes him look younger, somehow. 

“Nah. I don’t think so.” 

What did Cross do to deserve someone like Sans? His hips stutter and abruptly stop completely as another orgasm takes him over. Sans talks him through it, murmuring soft words as he twitches and shudders violently. 

“Sans.” He whines after it’s over. Unfortunately, he’s not quite satisfied yet. “I want you to cum inside me, please.” 

“Oh, to be young again.” Sans hums. “Go on, make me cum then.” 

No need to tell him twice. He starts to bounce again, this time much more vigorous. The sooner Cross has Sans’ cum inside him, the happier he’ll be. Sans seems happy to ride along. He closes his eyes and strokes Cross’ thighs. Occasionally, he rolls his hips along with Cross’. He’s not the most active, but Sans never is. Cross wouldn’t have it any other way. 

“Come on,” Cross urges. “Cum inside. Put a baby in me.” 

Sans eyes snap back open. “Cross-“ 

“Don’t you want that? Don’t you want to see me round and full of your baby?” He babbles, fucking himself on Sans’ cock harder and harder. “And when I pop it out, you can put another one inside me. Keep me yours  _ forever _ .”

“Holy shit.” Sans chokes out. “Cross, I’m gunna-“ 

“Yes! Yes, give it to me!” He redoubles his efforts, bouncing so fast that he’s nothing more than a blur. Sans writhes beneath him and his cock gives a strong twitch before warmth floods Cross.

But Cross doesn’t stop. 

He keeps going, milking Sans for every last drop he can get. He can feel every pulse and throb. It’s amazing, the best thing Cross has felt in his life. He doesn’t ever want to stop. But Sans weakly paws at him. 

“Buddy, too much, my dick is going to fall off.” Sans grunts. His body is trembling violently from the stimulation. A closer look at Sans reveals tears welling up in the corner of his eye sockets. In Sans’ own words, he gets leaky when he’s physically overwhelmed. 

If Cross was a meaner person, he’d keep going just to see the way he cries. But he takes pity on the older skeleton. Sans sighs in relief when Cross pulls off with a wet squelch. Strings of slick and cum keep them connected. Unable to help himself, Cross slides a finger inside of his cunt to feel how ruined it is. 

“Gross.” Sans mumbles sleepily. 

Cross huffs and pulls his finger away from his slick cunt. “Not as gross as you.” 

“Mmm.” 

He frowns. “Are you going to fall asleep again?” 

“Mmm.” Sans repeats, eyes already closed.

“At least take a shower with me.” 

“Rag.” Sans answers bluntly. “Shower in the morning.” 

“You’re going to wake up with a crusty dick my dude.” Sadly, it’d be far from the first time Sans fell asleep before they got clean enough for bed. 

A couple beats of silence and then one of those god awful snores grate at Cross’ ears. With a sigh, Cross crawls out of bed and stumbles to the bathroom in search of a rag. He can’t let Sans fall asleep dirty, because then he’ll feel guilty about it in the morning. 

Although, he can’t help but wonder if he could get away with more fun tonight. Sans does sleep pretty hard after cumming...

**Author's Note:**

> Twitter is @ snasational
> 
> This is part of the Paper Thin verse btw! It’ll fit in when I get around to posting more haha


End file.
